[Ossifying fibroma of the cranial vault. Case report]

A 68-year-old female was admitted with mild headache in the right frontal region. Physical and neurological findings were normal. Plain X-rays revealed a poorly circumscribed, osteoblastic lesion in the right frontal bone. Computed tomography scan showed that the diploic space was destroyed but that the inner and outer tables were intact. On 99mTc bone scan, a hot lesion was visible in the same region. The lesion was expressed as a low-signal intensity area on T1-weighted magnetic resonance (MR) image and as a high-signal intensity area on T2-weighted MR image. The tumor was broadly resected together with peripheral normal bone, and cranioplasty using a resin plate was performed. The tumor was mainly composed of mature, regularly aligned bone (lamellar bone) and intermingled fibrous tissue. Ossifying fibroma is a rare, benign fibro-osseous tumor that mainly involves the craniofacial bone. A few cases involving the cranial vault alone have been reported. The relevant literature is reviewed, and discussion focuses on the differential diagnosis between ossifying fibroma and monostotic fibrous dysplasia.